Posted by David Sherman on Wednesday, November 28, 2007 at 11:40:37 :
In Reply to: Re: Heat riser? not needed for full throttle posted by chriscase on Wednesday, November 28, 2007 at 09:36:58 :
Some have electrical heaters under the carb too. I suspect electrical and water are more accurately controllable with some sort of thermostatic device, and if you're making a header, it frees you up from having to connect the intake and exhaust in a heat riser and then deal with the differential expansion of the two fabricated assemblies. The heat riser method was probably cheaper in the factory due to less parts, since all it takes is a slightly different shaped casting, 4 bolts,and a gasket. The other advantage of a heat riser is it will heat up quicker. The exhaust goes right up under the carb so it will start to heat up the moment you start the engine, without waiting for the water to get warm. I wonder how they do it on airplanes that have a manual "carb heat" control.